The invention relates to a drive unit for the adjustment of the zoom, focus or iris ring of a camera lens.
The adjustment of the iris diaphragm aperture, the sharpness (focus), and the focal length (zoom) of a camera lens is carried out by means of lens rings which are positioned accordingly. For an easy and reliable positioning of the lens rings, drive units are used which are disposed vertically or horizontally at a camera lens. Each motor unit is coupled via a pinion or the like to the external teeth of a lens ring and may thus cause a setting of the lens ring.
However, frequently the problem arises that during the positioning of a lens ring the lens ring is displaced in an axial direction leading to a condition in which the pinion of the respective motor unit is not able to engage in the external teeth of the lens ring anymore. Thus, a further adjustment of the lens ring is not possible.
This problem especially arises if narrow lens rings or narrow pinions are used. However, the cramped building space around a camera often requires the lens rings and the pinions to be narrow.
The described problem particularly arises with regard to narrowly designed iris rings situated in front of the focus ring of a camera lens with a fixed focal length. When adjusting the focus, the iris ring may easily move out of the zone in which the pinion of the drive unit for adjusting the iris diaphragm is able to engage the external teeth of the iris ring.
Depending on the type of lens ring, the described problem may also occur at the zoom ring, the focus ring or an iris ring arranged behind the zoom ring or the focus ring.